Feed your plants weekly. Nitrogen, the engine of plant growth, is water soluble and as you water your containers from the top the dissolved nitrogen is leaving from the bottom. I use a fish-emulsion liquid feed with seaweed to provide all the trace nutrients my plants require and recommend it highly. You can use any liquid plant food (like Miracle Grow or Shultz) to promote growth. Compost tea is the Cadillac of liquid plant food and if you make your own compost tea, your plants will respond with bigger and better blooms as well as increased vigour.
And finally, no matter the size of the container, it is important to soak it all the way to the bottom at each watering. Continue watering until water emerges from the pot bottom. This ensures the roots can reach all parts of the container and grow properly.